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Transverse relaxation time ( T 2 ) mapping in the brain with off‐resonance correction using phase‐cycled steady‐state free precession imaging
Author(s) -
Deoni Sean C.L.
Publication year - 2009
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.21849
Subject(s) - flip angle , precession , pulse (music) , phase (matter) , nuclear magnetic resonance , magnetic resonance imaging , physics , artifact (error) , relaxation (psychology) , steady state free precession imaging , signal (programming language) , resonance (particle physics) , isotropy , imaging phantom , computer science , optics , atomic physics , computer vision , medicine , quantum mechanics , astronomy , detector , radiology , programming language , psychology , social psychology
Purpose To investigate a new approach for more completely accounting for off‐resonance affects in the DESPOT2 (driven equilibrium single pulse observation of T 2 ) mapping technique. Materials and Methods The DESPOT2 method derives T 2 information from fully balanced steady‐state free precession (bSSFP) images acquired over multiple flip angles. Off‐resonance affects, which present as bands of altered signal intensity throughout the bSSFP images, results in erroneous T 2 values in the corresponding calculated maps. Radiofrequency (RF) phase‐cycling, in which the phase of the RF pulse is incremented along the pulse train, offers a potential method for eliminating these artifacts. In this work we present a general method, referred to as DESPOT2, with full modeling (DESPOT2‐FM), for deriving T 2 , as well as off‐resonance frequency, from dual flip angle bSSFP data acquired with two RF phase increments. Results The method is demonstrated in vivo through the acquisition of whole‐brain, 1 mm 3 isotropic T 2 maps at 3T and shown to provide near artifact‐free maps, even in areas with steep susceptibility‐induced gradients. Conclusion DESPOT2‐FM offers an efficient method for acquiring high spatial resolution, whole‐brain T 2 maps at 3T with high precision and free of artifact. J. Magn. Reson. Imaging 2009;30:411–417. © 2009 Wiley‐Liss, Inc.